1. Field of the Invention
The invention relates to a collision type identifying device used in activating a passenger protection system of a vehicle.
2. Description of the Related Art
According to the related art, a passenger protection system such as an air bag system installed in a vehicle is designed such that the timing for activation, the deployment output of an inflator, or the like is adjusted on the basis of time-based changes in the deceleration detected by a deceleration meter or the like disposed in the vehicle.
It is to be noted, however, that there are various vehicle collision types as shown in FIGS. 1A to 1D. In the case of a head-on collision (A), the front face of a vehicle 1 collides against an object 2. In the case of an oblique collision (B), the vehicle 1 collides against an object 3 at a certain angle. In the case of a pole collision (C), the front center of the vehicle 1 collides against a telegraph pole 4 or the like. In the case of an offset collision (D), one side of the front face of the vehicle 1 collides against an object 5.
While the head-on collision (A) and the pole collision (C) are classified into a laterally symmetrical collision type, the oblique collision (B) and the offset collision (D) are classified into a laterally asymmetrical collision type. The direction, amount, timing, or the like of displacement of passengers in the event of a vehicle collision differs depending on whether the collision is symmetrical or asymmetrical. Furthermore, the offset collision (D) is classified into ORB (Offset Rigid Barrier) and ODB (Offset Deformable Barrier). In the case of ORB, the vehicle 1 collides against a rigid object. In the case of ODB, the vehicle 1 collides against a deformable object. The direction, amount, timing, or the like of displacement of passengers also differs depending on whether the offset collision (D) is ORB or ODB.
Accordingly, there is a limit to the aptness in driving the passenger protection system simply on the basis of time-based deceleration changes occurring in the vehicle. That is, although reliable detection of a vehicle collision type leads to the driving of the passenger protection system at a suitable timing and thus to the protection of passengers, it is difficult to detect a collision type precisely.
To overcome the difficulty, the present applicant proposes devices for identifying a vehicle collision type. In one of them (Japanese Patent Application Laid-Open 2001-30873), deceleration sensors (satellite sensors) are disposed at a plurality of locations in a vehicle in addition to a deceleration sensor (floor sensor) disposed on the center side of a main body of the vehicle. A collision type is identified on the basis of decelerations detected by these sensors and is utilized to control the timing suited to ignite an air bag system or an output state of the air bag. Thus, passengers are protected reliably. If a vehicle is equipped with the device thus constructed, passengers can be protected in accordance with the vehicle collision type and thus more reliably in comparison with the former case.
However, the vehicle deceleration at which the passenger protection system is to be activated in the event of an oblique collision or an ODB collision is often close to the vehicle deceleration at which the passenger protection system is not to be activated in the event of an ORB collision. Similarly, the vehicle deceleration at which the passenger protection system is to be activated in the event of a pole collision is often close to the vehicle deceleration at which the passenger protection system is not to be activated in the event of a head-on collision. In many cases, it is still difficult to identify a vehicle collision type with high precision simply on the basis of a vehicle deceleration.
As shown in FIGS. 1A to 1D, vehicle collision types are classified into symmetrical collision types and asymmetrical collision types. Furthermore, the vehicle may collide against objects with different rigidities. Thus, more precise identification of a collision type inevitably requires a plurality of identification processings.